The present invention relates to elevator systems having flat belts supporting the elevator car.
Elevator systems of the kind according to the present invention usually include an elevator car and a counterweight which are movable in an elevator shaft or along free-standing guide devices. The guide device for the elevator car in that case consists on the one hand of guide rails which are arranged in a fixed position in the elevator shaft at one side of the elevator car and on the other hand of car guide rails fastened to a side of the elevator car. For producing the movement, the elevator system includes at least one drive with at least one respective drive pulley which by way of support and drive means supports the elevator car and the counterweight and transmits the necessary drive forces to these.
The support means or drive means are termed support means in the following description.
In the case of conventional elevator systems, steel cables with a round cross-section are usually used as support means. However, flat, belt-like support means are increasingly used for more modem systems.
An elevator system according to the cantilever principle with flat-belt-like support means is described in the technical article “Hannover Messe: Neue Idee von ContiTech-Hubgurte für Aufzüge” (ContiTech initiativ, January 1998).
The article discloses an elevator for automobile body works in which a guide device, which comprises two guide columns, with integrated counterweight is present on one side of an elevating platform. At the upper end the two guide columns are connected together by a platform on which a drive motor is arranged, which acts by way of two drive pulleys on two flat support means strands by which the elevating platform and the counterweight can be moved upwardly and downwardly along the guide columns. In each instance one of the flat-belt-like support means is connected, on the side of the elevating platform facing the guide device, with the platform and extends from this support means fixing point vertically upwards to the side, which faces the elevating platform, of the periphery of the associated drive pulley, loops around this through 180° and then runs vertically downwards to a second support means fixing point present at the counterweight.
A drawing in the mentioned technical article indicates that with use of the same technique a passenger elevator car can also be moved instead of the elevating platform.
For simplification, in the following there is used, instead of different expressions for the form of elevator receiving means, only the term “elevator car” which refers exclusively to load receiving means in a “cantilever arrangement”.
An elevator system as described in the foregoing has, thanks to the use of flat-belt-like support means, the advantage that drive pulleys as well as deflecting rollers and support rollers can be used with a substantially smaller diameter than would be allowed in the case of use of a conventional wire cable. As a consequence of the smaller drive pulley diameter the drive torque required at the drive pulley is reduced, whereby a drive motor with smaller dimensions can be used. Due to this and thanks to the generally smaller support means pulley diameter, particularly space-saving elevator systems can be realized.
However, such elevator systems have certain disadvantages.
As a consequence of the small drive pulley diameter and because, in the case of the use of flat belts as support means known measures for improving traction capability, for example undercutting of the cable grooves at the drive pulleys for round support means, are not usable, the problem can arise in the case of a relatively large weight ratio between fully laden and empty elevating platform or elevator car that the traction forces transmissible between drive pulley and flat-belt-like traction means are not sufficient.
In addition, it is known that in the case of use of flat-belt-like support means without profiling the running surface, significant problems arise with lateral guidance of the support means on the drive pulley and, if they should be present, deflecting rollers and support rollers. Experience has shown that there is the risk that the support means rubs so strongly against the lateral boundary discs, which are usually present at the drive pulleys, deflecting rollers and support rollers, that the support means are damaged.